Design patterns provide solutions to the commonly occurring problems in the design of the software. The design pattern is like a blueprint that can be customized to target any particular problem of the code. Patterns are a toolkit of solutions to address common problems in software design. They provide the team with a common language to communicate efficiently.
Singleton design pattern in C# is one of the most widely used design patterns. In this pattern, only one instance of a class is created and it becomes a global point from where that class can be accessed. In simple words, a singleton is a class where only a single instance of the class is created and that access has simple access to the class.
Singleton pattern can be implemented in various ways in C#. Common characteristics of a singleton pattern are as follows.
- Private and parameterless single constructor.
- Sealed class.
- Static variable to hold a reference to the single created instance.
- A public and static way of getting the reference to the created instance.
Advantages of Singleton Design Pattern are listed below:
- Singleton patterns can implement interfaces.
- It has Static Initialization and can be lazy-loaded.
- It helps to hide dependencies.
- It is easy to maintain as it provides a single point of access to a particular instance.
There are a few disadvantages of using the singleton pattern which are mentioned below:
- Unit testing of the application becomes a bit difficult as it introduces a global state into an application.
- Parallelism within the program also gets affected due to the dependency on a single instance.
Singleton class vs. Static methods:
Classes with static methods cannot be initialized. We can reference a static method with the name of the class. The same copy of that static method is shared between every reference. So, changes made by one will be reflected in another.
Comparison is listed below between Singleton class and Static methods
- We can extend a singleton class but we can not extend a static Class.
- We can initialize a singleton class but a Static Class cannot be initialized.
- When the program containing the static class is loaded, then that static class is loaded automatically by the CLR.
Singleton Pattern can be implemented in several ways in C# as listed below:
- No Thread Safe Singleton.
- Thread-Safety Singleton.
- Thread-Safety Singleton using Double-Check Locking.
- Thread-safe without a lock.
- Using .NET 4’s Lazy<T> type.
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